1. Field of the Invention
The present invention relates generally to a device for creating drain channels in the soil, such as in golf courses, athletic fields, parks, and the like, and more particularly to reciprocating mechanisms of this type which minimize damage to the turf surface.
2. Description of Prior Art
In grass fields and other lawn areas which experience sustained vehicular and pedestrian traffic, the turf surface and underlying soil can become undesirably compacted. The problems associated with soil compaction are that rain and fertilizing chemicals are prevented from fully penetrating the ground. The short-term effect of such a condition is that the field will remain soggy for longer periods after a rain, and the long-term effect is the prevention of deep and healthy root systems and proper grass growth. Turf aeration is the process of creating channels in the soil so that water, air, and fertilizers can penetrate the ground and be dispersed effectively throughout the soil.
Over the years, many devices have been developed to alleviate soil-compaction problems ranging from pitchforks to heavy, tractor-driven machinery having multiple, reciprocating tines. One such device is shown in the British Patent No. 661,287 issued to Rose (hereinafter "Rose"). That reference discloses a turf aerator mechanism which is enclosed within a housing and which is guided by an operator walking behind the device. The turf aeration mechanism comprises a belt-driven drive link and a connecting rod which act to reciprocate another link member having a pivotable set of tines at one end. A rubber spring is attached on one end to the housing and on its opposite end to the tine support. The rubber spring urges the tines against a stop member which is also attached to the housing. The primary advantage claimed by Rose is that the path of the tines in penetration into and withdrawal from the ground is caused to remain substantially constant, thus minimizing damage to the turf surface.
Another commercial device common in the industry today is the turf aerator manufactured by Verti-Drain.RTM. under U.S. Pat. No. 4,422,510 issued to de Ridder (hereinafter "de Ridder"). That device teaches a frame which supports several rotary shafts, drive links, and connecting rods which reciprocate a number of pantograph-type mechanisms. In each mechanism, a tine holder having soil-piercing tines is pivotally attached to an upper link in the mechanism, and a lower link supports a spring device which allows the tines to rotate within the soil to create a drain channel. The device is typically powered by the power take-off drive of the pulling tractor. The chief advantage claimed by that reference is that the turf surface remains largely undisturbed because of the manner in which the path of the tines is substantially vertical during penetration and withdrawal due to the action of the pantograph mechanism.
A number of deficiencies exist, however, in the device disclosed in the de Ridder patent. First, the complexity of the pantograph mechanism in effecting the proper soil penetration and creation of drain channels is largely unnecessary based on Applicant's practical experience. The three factors which most influence successful turf aeration are: (1) the initial angle of penetration of the tines, (2) the pivoting action of the tines while they are in the soil, and (3) the angle of withdrawal of the tines. All three of these factors can still be achieved with a simpler, less expensive device. In particular, it is desirable to have an aeration machine which can match tine length to soil condition. However, changing tine length requires a means for adjusting the resting angle of the tines to insure that the tines penetrate the soil substantially perpendicular to the soil.
Second, the reciprocating mechanisms of the de Ridder device are not dynamically balanced. During operation, the entire machine, as well as the pulling vehicle, are intolerably shaken at higher speeds because of the unbalanced components. This vibration inevitably leads to discomfort to the operator and frequent replacement of expensive machine parts. Moreover, because the speed of operation is relatively slow due to such vibration, the aeration process takes longer and is more expensive to complete. Third, the existing aerator mechanisms are driven by the power take-off drive of the tractor through a single point of attachment to the aerator drive shaft. Smoother operation and use of less bulky parts can be achieved dividing and balancing the drive load on the aerator drive shaft.
With regard to the Rose patent, that device is ill-suited to large scale commercial use, primarily because it is not designed to be pulled behind a tractor and operated through a power take-off drive. Therefore, there is a definite need for a turf aeration device which (1) can be used in commercial groundskeeping environments, (2) can be operated more comfortably and at higher speeds through balanced operation, (3) is capable of producing effective drain channels comparable to those of existing machines, (4) is simpler and less expensive to maintain and repair, and (5) can adjust the angle of tine entry into the ground to accommodate various lengths of tines.